The overall goal of this proposal is to perform high throughput screening assays (HTS) to identify inhibitors for SUMOylation. Protein modification by the SUMO (Small Ubiquitin-like MOdifier) family of proteins has recently been established as an important post- translational modification that plays an essential role in many functions including gene transcription, cell cycle progression, DNA repair, viral and bacterial infection, and the development of neurodegenerative diseases. Inhibitors of SUMOylation will serve as much needed reagents for investigating the role of SUMOylation in different cellular functions, which remain largely unclear. The inhibitors will also have therapeutic potential for diseases, such as cancer and viral infection. However, such inhibitors have not been reported and are not yet available to the scientific community. We have developed several assays to identify such inhibitors. The primary HTS assay uses the ALPHA screening technology. The secondary screening assay uses fluorescence resonance energy transfer (FRET) to eliminate false positive hits obtained in the ALPHA screen. Additionally, an ubiquitination assay will be used to identify the hits that are specific for inhibiting SUMOylation and not other ubiquitin-like modification systems. The immediate applications of the inhibitors identified in the screen are: 1) to probe the role of SUMOylation in different cellular functions, such as in the DNA repair pathways, 2) to test the inhibitors in cellular and animal models of diseases where SUMOylation has been shown to play important roles, such as in cancer and viral infections. Our long term goal is to develop potent SUMOylation inhibitors based on the structure-activity relationship studies of the hits identified from this study. Inhibitors of the homologous ubiquitin-proteosome pathway have been critical in dissecting the role of the ubiquitin-proteosome pathway in many cellular functions and are surprisingly successful as anti-cancer therapeutic agents. SUMOylation inhibitors hold similar promise in having a broad impact in research and could lead to the establishment of a new paradigm in developing therapeutic agents for devastating diseases, such as cancer and infectious diseases. PUBLIC HEALTH RELEVANCE: [unreadable] The overall goal of this proposal is to perform high throughput screening assays (HTS) to identify inhibitors for SUMOylation. [unreadable] [unreadable] [unreadable]